Thrust block curing time

[BernieH]

AWWA stipulates that thrust blocks must cure for 5 days before a water main is pressure tested (unless high-early is used). However, I understand that some contractors are routinely pressure testing immediately, without waiting for curing to occur. What is your experience with what is actually happening in the field? How diligent should we be in our enforcement of the 5-day rule?
Thanks

 

[bimr]

The use of thrust blocks become very problematic for the reason that you bring up as well as considerations.

Most of the time, the Contractors take a risk and move on taking shortcuts on the installation. Most of the time it work out, but not always.

The use of thrust blocks should be considered with great care. They are only as good as the stability of the soil. In locations where the soil may be disturbed by future construction, reliance on thrust blocks, particularly for large diameter pipe, is not a very good idea. The use of restrained joints and trench friction is a better idea.

 

[bimr]

Here is reference for your consideration:

http://www.ebaa.com/PDF/Connections.PD-01.pdf

 

[rconner]

While I guess I have seen many specific Engineer’s contract documents over the years that mention some curing time etc. of thrust blocks, I guess I have missed that “AWWA” had gotten into these issues with a minimum “5-day” limit. I am curious what is the specific “AWWA” reference? In any case, while the compressive stress actually applied to the concrete might in many cases be less than in many common structural applications, it certainly makes sense that load should not be applied until the concrete reaches a level of strength that can dependably withstand the load application involved. When that (or standard containing same) is duly specified in contract documents, I would think the Contractor could be at risk not conforming to same.